Field of the Invention
The invention relates to a fiber metal laminate comprising metal layers and fiber reinforced plastic layers in between said metal layers, wherein the metal layers and the fiber reinforced plastic layers are bonded together, and wherein the fibers of the fiber reinforced plastic layers are arranged in a first group and in a second group whereby the fibers of the first group are at an angle with respect to the fibers of the second group.
Description of Related Art
The invention relates further to an aircraft wing embodied with one or more of such fiber metal laminates.
A fiber metal laminate according to the preamble is known from U.S. Pat. No. 5,547,735. This known fiber metal laminate comprises a bidirectional reinforcing layer containing about 45-70 volume percent high-strength glass fibers. The bidirectional reinforcing layer includes a center layer containing glass fibers oriented generally parallel to a first direction; and first and second outer layers each reinforced with glass fibers oriented in a second direction extending generally transverse to the first direction. The bidirectional laminate is suitable for use in aircraft flooring and other applications requiring improved impact strength.
WO2004/071761 discloses a laminate of at least two plates formed from an aluminium alloy, which each have a thickness of less than 1 mm and between which is situated an intermediate layer on the basis of plastic which is connected to the metal plates and contains at least two groups of preferably continuous, mutually parallel fibers whereby the fibers of the two different groups intersect preferably at an angle of about 90 degrees. The fibers may be made of aromatic polyamide, glass or carbon. The laminate according to this citation may be applied as skin plate for the body of an aircraft or spacecraft.
The prior art is silent on the use and the associated problems when a fiber metal laminate is to be used as a skin panel for an aircraft wing.
Aircraft wing structures which are known to comprise upper wing skin panels and lower wing skin panels are predominantly loaded by upward fatigue bending and torsional loading. For the lower wing skin panels of the aircraft wing this implies uni-axial tensile loads and shear loads.
To meet the uni-axial tensile loads and to provide sufficient bending stiffness and strength to the laminate and to the aircraft wing in which the laminate is applied, it is known to use a fiber metal laminate having the fibers oriented in the wingspan direction. The problem is however that then the shear stiffness and shear strength is low.
It has also been proposed to orient the fibers in the fiber metal laminate at an angle of for instance 45 degrees, yet this goes at the expense of a reduced bending stiffness and strength.
As a further alternative it has been proposed to diminish the volume of the fiber reinforced plastic layers in favor of the volume of the metal layers, which are usually made out of aluminium. The aluminium layers exhibit a higher shear stiffness, but this solution reduces the fatigue performance of the laminate in comparison with a regular fiber metal laminate significantly.